What is the best term for histamine?

The best term for histamine is biogenic amine.

Biogenic amines are organic bases that are found in living organisms. They are formed by the decarboxylation of amino acids. Histamine is a biogenic amine that is produced by the decarboxylation of histidine. It is involved in a variety of physiological processes, including inflammation, allergic reactions, and neurotransmission.